Telephone trunking system.



G. S. WINSTON. TELEPHONE TRUNKING SYSTEM. APPLICATION FILED NOV. 17,1906.

Patented Oct. 4, 1910.

5N1 ATES ATNT ton CHARLES S. WINSTON, OF CHICAGO, ILLINOIS, ASSIGNOR TOKELLOGG SWITCHBOARD AND SUPPLY COMPANY, OF CHICAGO, ILLINOIS, ACORPORATION OF ILLINOIS.

TELEPHONE TBUNKING SYSTEM.

Application filed November 17, 1906.

Specification of Letters Patent.

Patented Oct. at, 1910.

Serial No. 343,801.

To all whom it may concern:

Be it known that I, Crmnnns S. WVIN STON, a citizen of the UnitedStates, residing in Chicago, county of Cook, and State of Illinois, haveinvented certain new and useful Improvements in Telephone TrunkingSystems, of which the following is a specification.

My invention relates to trunking systems adapted to be used between tollconnecting cords and common battery subscribers lines, and has, amongother objects, the provision of simple means for placing the connectionof ringing current with the desired line entirely under the control ofthe toll operator, and for relieving the trunk operator of allunnecessary attention to, or supervision of the connection. It has beencustomary in the past for the toll operator to order the connection andfor the trunk operator to then test the desired line, insert the trunkplug in the jack, and to operate her ringing key, and to furthersupervise the connection until the desired party has answered his call.

By the present invention the trunk operator is relieved of all dutyfurther than testing the desired line and inserting and withdrawing thetrunk plug.

Other features of my invention will be hereinafter described andclaimed, reference being had to the accompanying drawing forming a partof this specification.

Referring to the drawing, a toll line 1 is shown terminating in a localbattery subscribers station with. the usual telephone apparatus,including a transmitter 2, local battery 8 and primary of an inductioncoil 4, adapted to be included in a local circuit by the removal of thereceiver from the hook 6, the annunciator bell 7 being normally bridged.across the line and the generator 8 being adapted to send current overthe line to the central oiiice, where it actuates the drop 9 or othersuitable signal to attract the attention of the toll operator.

The usual toll. cord extending in two limbs 10 and 11 is adapted toconnect with the toll line and has bridged between its limbs any desiredclearing-out signal, here shown as a relay 12, controlling the localcircuit of supervisory lamp 13. A listening key 14 is adapted to connectthe operators receiver 15, secondary of the induction coil 16 andcondenser 17 in series between the limbs of the toll cord. A transmitter18 is connected in series with the primary of induction coil 16, andwith any suitable source of exciting current. The ringing key 1.9 isadapted by its actuation to place ringing current upon one limb of thecalling end of the cord and to connect the other limb with ground oranother suitable third conductor.

The trunk line 20 extends from the jack 21 at the main otlice in twolimbs 22 and 23 to the windings 2% and 25 of the induction coil 26 atthe auxiliary oflice. From the inner terminal of winding 24: of theinduction coil the conductor 27 extends through the normal contacts 28of relay 29 and through the high resistance and impedance 30 to ground,while from the inner terminal of the winding 25 the conductor 31 extendsto the normally open contact of the relay 29. From a point on conductor22 outside the winding 25 of the induction coil conductor 32 extendsthrough the normal contact 33 of relay 29, thence through conductor 34,coil of relay 35, conductor 36, normal contact 37 of relay 38 to thelive pole of battery 39. The other windings 10 and a l of the repeat ingcoil 26 are inductively connected at their inner ends by the condenser12, the outer ends being permanently connected with the talking strandsand 1 1 of the incoming end of the trunk which terminates in thecontacts of the calling plug 455. The live pole of battery 39 isconnected through the coil of relay 38 to conductor 4. 1, while thegrounded pole of the battery is connected through the coil of relay 16to conductor 13. The signal s7 has its circuit controlled by contacts ofrelays 35, 16 and 38, being normally connected by conductors 18 and 19to an open contact of relay 38. The conductor is normally connected withthe live pole of the battery by contacts of relay 38, and normallydisconnected from the signal by contacts of relay 35. The relay 29,controlling the connection between coils 24 and 25 of the induction coil26, is adapted to be actuated over a local circuit, normally broken bythe contacts of relays 4:6 and 38, and is adapted to be energized bycurrent from the battery 89. The coil of relay 51, which is ofcomparatively low resistance, has one of its terminals connected throughconductor 52 to a normally open contact of relay 38 where it may beconnected in series with conductor 36, which is normally in series withthe outgoing end of the trunk. The other terminal of the coil of relay51 is connected by conductor with the live pole of the battery. A sourceof ringing current is connected with one limb of the calling end of thetrunk circuit by the actuation of armature of relay 51 while currentfrom the live pole of battery 39 is connected to the other limb throughthe non-inductive resistance 56 by the actuation of armature 5st, thenormally closed contact with armature being then broken to preventringing current from being impressed upon the coil of relay 16.

An operators set comprising an induction coil 57, receiver 53, condenser59 and transmitter 60 enables the trunk operator to re ceive the orderfrom the toll operator and to receive the busy test through the normallyopen contacts of the key 61.

The plug 15 is adapted to connect with the jack 62 ot' a common batterytelephone line extending in limbs 63 and 6st to the substation where theannunciator bell 65 and condenser 66 are normally bridged across thecircuit. The transmitter 67 and receiver 68 are normally in an openbridge, of the line conductors, which is adapted to be closed by theactuation of the switch 69. At the central otiice the line signal 70 andline relay 71 are normally associated with the line for signaling in theusual manner while the cut-ott relay 73 is adapted by its actuation todisconnect the signaling apparatus and connect the limbs of thetelephone line directly with the jack.

In the operation of this system a call is sent in from the generator 8over the toll line 1 and actuates the drop 9 before the toll operator.Upon observing the signal the operator connects the answering plug ofone of her toll cords with the calling line and throws her listening keylet to obtain the number of the desired subscribers station. Uponlearning the desired number the operator presses her order button andnotifies the trunk operator of the desired line. The trunk operator thenresponds by telling the toll operator to connect with one of her idletrunk lines which may be connected with jack 21 and at the same timethrows her test key 61 and tests the jack 62 of the desired line whichmay be multipled before a plurality of operators positions. It the lineis busy the sleeve or test contact of the jack will be at a potentialhigher than that of ground, and a current will then flow through thetertiary ot' the induction coil 57, thus causing an inductive click inthe operators receiver.

Finding the line idle the trunk operator inserts plug 45 in the jack 62,thus closing a local circuit from the battery 39 through the coil ofrelay 38, conductor 44:, sleeve contacts of the plug and jack, andthrough the coil of the cut-olt' relay 73. The current in this pathactuates the relays 38 and '73, the former closing a local circuit fromthe battery 39 over conductors a9 and 43 and through the signal a? todisplay said signal, and the latter disconnecting the line relay T1 andplacing the line in condition to be called. In the meantime the trunkoperator has inserted her calling plug in the jack 21, thus closing acircuit which may now be traced from the live pole of battery 39 overcoir ductor 53, through the coil of relay 51, conductors 52 and 36, thecoil of relay 35, conductors 3 1, 32 and 22, the sleeve of jack 21, limb11 of the toll cord, the coil of relay 12, limb 10 of the toll cord, tipof jack 21, conductor 23, winding 241 of the induction coil 26,conductor 27, contacts 28 and the high resistance and impedance 30 backto the ground pole of battery 39. The current in this path is sufficientto actuate the relays 35 and 12 which are of comparatively highresistance, but owing to the extremely high resistance of coil 30 thecurrent is not suflicient to actuate the relay 51 which is of lowresistance. The actuation of relay 35 new opens the circuit of signal47, thus extinguishing it. If, however, the toll operator inserts herplug before the trunk operator has made connection with the desired linethe relay 35 is actuated over the same path as previously describedexcept that its circuit excludes the relay 51. The actuation of relay 35connects the signal 17 in a local circuit with the battery 39 includingconductor 50 and normal contacts of relay 38. Thus the signal 47 isdisplayed when connection exists at either end of the trunk, but isettaced when connection exists at both ends.

The toll operator now throws her ringing key 19, placing a ground uponthe sleeve side of the trunk line which decreases the resistance of thedescribed path, including the coil of relay 51 by removing the highresistance 30, the winding 2st of the induction coil 26 and the coil ofrelay 12 from the previously described circuit. Current now flows frombattery through conductor 53, the coil of relay 51, conductors and 36,the coil of relay 35, conductors 3st, 32- and 22, the sleeve of jack 21and to ground through the spring of key 19. The current in this path issuflicient to actuate the relay 51, placing ringing current on thespring and battery upon the spring 54. 7

It will be noted that the toll operator may insert her plug in theoutgoing end of the trunk and throw her ringing key before the trunkoperator has connected with the desired line. To provide against placingthe ringing current upon a plug which may be in the trunk operators handunder these conditions, the circuit of relay 51 is maintained broken atcontacts of the sleeve supervisory relay 38 until after the plug hasbeen inserted in the jack of the desired line.

The actuation of relay 51 places the noninductive resistance 56 inparallel with the coil of relay 38. between the live pole of battery andthe sleeve strand 44 of the trunk cord. The resistance of the coil 56 isadjusted so as not to shunt the relay 38 sufficiently to allow it tofall back, but at the same time to furnish a path of low impedance forthe returning ringing current, thus preventing the deenergization orrattling of relays 7 3 and 38. The cut-oft relay being maintainedactuated the ringing current now flows over one limb of the called linethrough the annunciator and condenser 66, back over the outer limb ofthe called line and through battery to the generator by way of thenon-inductive resist-- ance 56. hen the ringing key 19 is again releasedthe path. for current through the relay 51 again includes the highresistance coil 30, winding 24 of the induction coil 26 and the coil ofrelay 12, which reduces the current enough to allow the low resistancerelay 51 to fall back and remove the ringing current from the calledline.

When the called subscriber answers his call current from the battery 39flows through the coil of relay 38, over the line and back to the groundside of battery 39 through the coil of relay 46. This current actuatesrelay 46, which in turn actuates relay 29 over a local circuit includingconductor 49. The actuation of relay 29 removes the coil of relay 35from its connection with the outgoing end of the trunk, and at the sametime short-circuits the inner terminals of windings 24 and 25 of therepeating coil 26. The connection of battery 39 is thus removed from theoutgoing end of the trunk and relay 12 falls back and extinguishes thesignal 13, thus indicating to the toll operator that the call has beenanswered. The deenergization of relay 35 would now again close thecircuit of signal 47 but that the actuation of relay 46 opened thecircuit of conductors 48 and 49 at the contacts of relay 46. The linesare now in condition for conversation, currents being fed to the commonbattery line through the coils of relays 38 and 46, and the signalsbefore both operators are eftaced. Then the called subscriber againplaces his receiver upon its hook and opens the circuit of relay 46relay 29 is simultaneously decnergized and current from battery 39 isagain sent over the line and through the coil of relay 12 as beforedescribed. This actuates the signal 13 before the toll opera tor and theconnection of the toll cord is severed from the trunk. Relay 35 nowfalls back and again closes the circuit of signal 47 notifying the trunkoperator that the conversation has terminated. She then removes her plug45 from its connection with the called line and all parts assume theirnormal condition ready for another call.

liile I have shown and described my improvements in connection with onlyone form of telephone systems I do not wish to limit the scope of myinvention to this specific arrangement, the improvements here disclosedbeing applicable to many other circuit arrangements.

Having thus described my invention what I claim and desire to secure byLetters Patent is:

1. In a telephone system, the combination with a trunk line, of a cordcircuit adapted to be connected with it at its outgoing end, and atelephone line with which its incoming end may be connected, a source ofdirect current associated with the incoming end of the trunk, means tocomplete a path for current from said source by the connection of thecord circuit with the trunk, a ringing key associated with the cordcircuit, means to vary the direct current flow from said source by theactuation of the ringing key, and a ringing relay at the incoming end ofthe trunk actuated by such change in the current flow, substantially asdescribed.

2. In a telephone system, the combination with a trunk line, of a cordcircuit adapted to be connected therewith at its outgoing end, and atelephone line with which its incoming end may be connected, a source ofdirect current, and a relay associated with the incoming end, anauxiliary circuit con trolled by said relay, a signal associated withthe cord circuit, a circuit completed through said relay by theconnection of the cord circuit with the trunk,'whereby said signal isdisplayed, but whereby said relay is not actuated, a ringing keyassociated with the cord circuit, and means for increasing the currentin said circuit, whereby said relay is actuated by the operation of saidringing key, substantially as described.

3. In a telephone system, the combination with a trunk line, of a cordcircuit adapted to be connectedtherewith at its outgoing end, and atelephone line with which its incoming end may be connected, a source ofdirect current associated with the incoming end of the trunk, a ringingrelay and a signaling relay connected in series between said source andthe outgoing end of the trunk when a connection is established betweenthe incoming end of the trunk and a SHbSCIlbQPS line, a circuitcompleted by the connection of the cord circuit with the outgoing end ofthe trunk, whereby the signaling relay is actuated, a ringing keyassociated with the cord circuit, and means to increase the current insaid circuit by the actuation of said ringing key, whereby the ringingrelay is actuated, and a source of ringing current associated with thecontacts of said ringing relay, substantially as described.

a. In a telephone system, the combination with a trunk line, of a cordcircuit adapted to be connected therewith at its outgoing end, and atelephone line with which its incoming end may be connected, at sourceof direct current associated with the incoming end of the trunk, a relayand a high resistance normally in series with said source and with theoutgoing end of the trunk when connection has been established with thetrunk at each end, and means associated with the cord circuit forshunting the high resistance, whereby the relay becomes operative, andan auxiliary circuit controlled by said relay, substantially asdescribed.

In a telephone system, the combination with a trunk line, of a cordcircuit adapted to be connected with it at its outgoing end, and atelephone line with which its incoming end may be connected, a source ofdirect current, a ringing relay and a high resistance adapted to beplaced in series when connection is established with each end of thetrunk, and means associated with the cord circuit for shunting the highresistance, whereby the ringing relay becomes operative, and a source ofringing current connected with the called line by the actuation of saidringing relay. substantially as described.

6. In a telephone system, the combination with a trunk line, of a cordcircuit adapted to be connected therewith at its outgoing end, and atelephone line with which its incoming end may be connected, at sourceof direct current associated with the incoming end of the trunk, a lowresistance relay, a signaling device and a high resistance adapted to beplaced in series with said source when a connection is established witheach end of the trunk, the current in said circuit being of sufficientstrength to actuate the signaling device, and means associated with thecord circuit for increasing the current, whereby the relay becomesactuated, and apparatus affected by the actuation of said relay,substantially as described.

7. In a telephone system, the combination with a trunk line, of a cordcircuit adapted to be connected therewith at its outgoing end, and atelephone line with which its incoming end may be connected, a highresistance and a relay associated with the incoming end of the trunk, apath for current from said source through said relay and high resistanceover the limbs of the outgoing end of the trunk in series, completed bythe connection of the cord circuit with the trunk, whereby said relaybecomes operative, a ringing relay adapted to have its coil included insaid path when a connection is established with the incoming end of thetrunk, the current in said path being normally insufficient for theoperation of said ringing relay, and means associated with the cordcircuit for increasing the current through said ringing relay, wherebysaid relay becomes operative, and a source of ringing current connectedwith the line by the actuation of said ringing relay, substantially asdescribed.

8. In a telephone system, the combination with a trunk line, of a cordcircuit adapted to be connected therewith at its outgoing end, and atelephone line with which its incoming end may be connected, a highresistance and a relay associated with the incoming end of the trunk, apath for current from said source through said relay and high resistanceover the limbs of the outgoing end of the trunk in series, completed bythe connection of the cord circuit with the trunk, whereby said relaybecomes operative, a ringing relay adapted to have its coil included insaid path when a connection is established with the incoming end of thetrunk, the current in said path being normally insufficient for theoperation of said ringing relay, and means for excluding said highresistance from said path for current, whereby the current in said pathis increased, and said ringing relay becomes operative, and a source ofringing current connected with the line by the operation of said ringingrelay, substantially as described.

9. In a telephone system, the combination with a trunk line, of a cordcircuit adapted to be connected therewith at its outgoing end, and atelephone line with which its incoming end may be connected, a highresistance and a. relay associated with the incoming end of the trunk, asource of current a path for current from said source through said relayand high resistance over the limbs of the outgoing end of the trunk inseries, completed by the connection of the cord circuit with the trunk,whereby said relay becomes operative, a source of ringing current aringing relay adapted to have its coil included in said direct currentpath when a connection is established with the incoming end of thetrunk, the current in said path being normally insufficient for theoperation of said ringing relay, and means for decreasing the resistanceof said path for current, whereby said ringing relay becomes operative,to connect said ringing current source with the desired line,substantially asdescribed.

10. In a telephone system, the combination with a trunk line, of a cordcircuit adapted to be connected therewith at its outgoing end, and atelephone line with which its incoming end may be connected, a highresistance and a relay associated with the incoming end of the trunk, apath for current from said source through said relay and high resistanceover the limbs of the outgoing end of the trunk in series, completed bythe connection of the cord circuit with the trunk, whereby said relaybecomes operative, a ringing relay adapted to have its coil included insaid path when a connection is established with the incoming end of thetrunk, the current in said path being normally insufficient for theoperation of said ringing relay, and means for closing a circuit overone limb only of the outgoing end of the trunk, whereby the current insaid path is increased and said ringing relay is operated and a sourceof ringing current connected with the desired line by the actuation ofsaid ringing relay, substantially as described.

11. In a telephone system, the combination with a trunk line, of a cordcircuit adapted to be connected therewith at its outgoing end, and atelephone line with which its incoming end may be connected, a source ofdirect current at the incoming end of the trunk, said source and a relayin series with the outgoing end of the trunk, and means for varying thecurrent through said relay, whereby it may become operative andtelephone apparatus affected by the operation of said relay,substantially as described.

12. In a telephone system, the combination with a telephone line, of aconnective circuit therefor, a source of direct current, a lowresistance relay winding, a high resistance relay winding and a highresistance in a circuit of said source, the current from said sourcethrough said path being suflicient to actuate said high resistance relaybut not sufficient to actuate said low resistance relay, telephoneapparatus controlled by the actuation of said high resistance relay,means to exclude said high resistance from said pat-h, whereby thecurrent is increased sufficiently to actuate said low resistance relay,and a source of ringing current con nected with the calling end of thetrunk circuit by the actuation of said low resistance relay,substantially as described.

Signed by me at Chicago, county of Cook, and State of Illinois, in thepresence of two witnesses.

CHARLES S. WINSTON.

Witnesses CLIrroRD (J. BRADBURY, EDITH F. GRIER.

